My Cerith snails lay eggs in paths like that all the time. They disappear in a few days. I've never noticed any new Cerith snails in the tank, so I'm either not providing the right environment for their development or they are getting eaten.

From the research I did at the time, it doesn't look like anyone has successfully raised ceriths to adulthood. It has something to do with their first phase in life where we don't have enough food of the right type to feed them.

Yeah, probably ceriths as I get that a lot in my tank. FWIW, I have found a couple tiny ceriths crawling around recently. Hard to say if they actually developed from the eggs or were just tiny ceriths coming in on a piece of coral or whatnot. In my old reef, I definitely had more snails than I started with but most of those were Stomatellas.....